A typical cutting process utilizes cutting fluid to discharge chips generated in the process. Among drills in the past that discharge the chips with the aid of the cutting fluid, there is a drill having an oil hole formed in a body for circulating the cutting fluid and a hole in communication with the oil hole, wherein a top end of the communication hole is opened into a chip discharge groove.
According to this drill, the cutting fluid having passed through the oil hole is discharged into the chip discharge groove from the communication hole and is guided along the chip discharge groove until it is eventually discharged therefrom to the outside together with the chips.
Meanwhile, there is a drill capable of discharging the chips without the use of the cutting fluid. For example, Patent Document 1 (Japanese Patent Application Laid-Open Publication No. S57-89511) discloses a drill having a chip discharging hole formed inside the body and an outlet port formed in communication with the chip discharging hole, wherein a top end of the outlet port is opened into a periphery of the body.
According to this drill, as the body of the drill starts rotating, newly generated chips entering the chip discharging hole slowly pushes out the old ones that had already circulated along the chip discharging hole through the outlet port.